1. Field of the Invention
This invention relates to infrared ("IR") imaging materials, films, methods, and systems, all of which include a polymeric semiconductor compound having an infrared absorption band crosslinked with a spiropyran capable of producing a visible absorption band. The materials, films, methods, and systems of the invention are adapted to produce a visible image when exposed to infrared radiation during use.
2. Description of Related Art
Existing commercial infrared imaging systems can generally be classified into two main categories:
a) Mechanical scanning systems that project sequentially each point of the IR image on a single detector. These systems commonly operate in the 10 microns range, having detectors which are cooled with liquid air or liquid nitrogen. PA1 b) Imaging tubes with an array of detectors, where the elements of the array are scanned with an electron beam. This category of imaging device generally operates in the near infrared, and uses an infrared source to illuminate the object.
Materials such as doped germanium, indium antimonide, or cadmium telluride are typically used for detection in the former case, and germanium or pyroelectric materials in the latter.
Systems as in (a) tend to be complicated, bulky, and expensive, and may require professional maintenance.
Systems as in (b) tend to be more compact and robust. Typically, they have no moving parts, which tends to simplify maintenance. However, their performance is generally limited to the near infrared.
In addition to the above systems, other systems have been described which include a dichroic liquid crystal coated on a membrane in order to detect IR at room temperatures. See U.S. Pat. No. 4,751,387, now U.S. Pat. No. Re. 33,914, the disclosure of which is incorporated herein by reference.
It is believed that this invention may be used to provide a high resolution static infrared camera capable of operating at room temperature. Such a camera would be desirable, especially for airborne and ground operations where volume and weight are important. Mechanical scanning systems generally require frequent maintenance and cooling. Imaging tubes may be more dependable, but generally are not operable in the far infrared range, and are generally limited in resolution by the size of the elements of the array. They also generally use cryogenic systems for cooling. The life time of cryogenic liquids is short and requires replenishment of cooling systems at relatively short intervals.
Accordingly, there is a continuing need to develop improved infrared imaging systems and materials. It is a general object of this invention to provide infrared imaging systems, materials, films, and methods which address at least some of the disadvantages experienced in the art.